The present invention relates to a syringe that reduces spray of fluid from the end of a syringe and the needle mounted to the end of the syringe.
Throughout the world, the re-use of hypodermic syringe products, which are intended for single-use only, is a problem which causes the transfer of contagious diseases. Intravenous drug users who routinely share and re-use syringes are a high-risk group with respect to the AIDS virus. Also, the effects of multiple syringe use are a major concern in some countries where the repeated use of syringe products during mass inoculation programs may be responsible for the spread of many diseases. Syringes are often recycled in developing countries without proper sterilization.
To alleviate these problems, syringes have been designed with collapsible plunger rods which render the syringe effectively unusable after its intended use. For example, as disclosed in U.S. Pat. No. 6,217,550 (Capes et. al), the entire content of which is incorporated herein by reference, the plunger rod is provided weak points so that when pressed with excessive force at the completion of an injection, the plunger breaks into two unusable parts. Thus, the user expels as much fluid as possible from the barrel of the syringe as would normally be done, and then presses hard upon the plunger thumb press to break the plunger rod. Syringes of this type, which are capable of being used only once, will be referred to herein as single use syringes.
In single use syringes, when the user breaks the plunger rod, the proximal part of the plunger rod moves forward at high speed into the distal part of the plunger rod. The collision between these parts creates an impulse that compresses the plunger, and which thus compresses whatever fluid may remain in the dead space between the plunger and roof of the barrel. This results in a spray of fluid from the nozzle of the syringe. As used herein, the nozzle of the syringe refers to the opening at the distal end of the syringe and/or the hollow needle located at the distal end of the syringe. The spray of fluid from the nozzle of a syringe may also be problematic in traditional syringes as well when a user presses on the thumb press of the plunger rod with excessive force. Such spraying poses a risk of spreading contaminated fluids, such as contaminated fluid blood. It would therefore be desirable to provide syringes, mechanisms and methods that reduce the spray from the nozzle of syringes, and in particular single use syringes.